1. Field of the Invention
The invention is directed at a method for supplying an entrained-flow gasification reactor with fuel from a storage container, with the interposition of at least one transfer container and at least one feed container, whereby gas that contains CO and H2 and flue ash is produced in the entrained-flow gasification reactor.
2. Description of the Related Art
In the transfer and feed of fine-grained to dust-form fuel with a gas that contains carbon dioxide, carbon monoxide, and oxygen, in an entrained-flow gasifier that is under pressure, in which finely divided or dust-form (<0.5 mm) fuels, for example coal, petcoke, biological wastes or fuels, are reacted with gasification agents that contain oxygen, in suspension, at a low particle charge (<50 kg/m3), at elevated pressure up to 10 MPa, at temperatures above the slag melting point, the gas that contains oxygen is supplied at a substoichiometric ratio, so that a product gas that contains carbon monoxide is produced.
Since the fuel is at first present under ambient pressure, it must first be brought to a pressure level above the reactor pressure, by way of the feed system, in order to then be transported to the burners of the pressurized gasification reactor in metered manner.
An advantageous method provides that the fuel is conveyed from a storage container into transfer containers. These are first pressurized to a pressure level above the reactor pressure, in order to then convey the fuel into a feed container for the burners of the gasification reactor, which is permanently under pressure, by way of a conveying line, by means of dense stream conveying. From this feed container, the burners are continuously supplied with a metered fuel mass stream, in each instance. The transport gas required to convey the dense stream is supplied in or in the vicinity of the outlet of the transfer container, or in the conveying line. The emptied transfer containers are then relaxed, in order to be able to take up another fuel batch, under approximately atmospheric pressure. The relaxation gas is dedusted and released into the atmosphere.
Usually, nitrogen from an air separation system or carbon dioxide is used for the transfer. Carbon dioxide is used if the gas to be produced is a synthesis gas low in nitrogen, or hydrogen, and/or CO.
Carbon dioxide can be obtained in the gas treatment that follows gasification. Frequently, the gas that flows out of the gasifier is dedusted and cleaned and subjected to CO conversion, in order to set the H2/CO ratio required by the synthesis, or in order to produce pure hydrogen. In this connection, CO and steam are converted to CO2 and hydrogen. Afterwards, the gas is cooled, the moisture is condensed out, and subsequently, CO2 is washed out in a washing process with circulating solvents, for example MDEA, Genosorb, or methanol. In a desorber, the CO2 is driven out of the solution by means of lowering the pressure or increasing the temperature. The gas obtained in this manner contains not only the CO2 but also other components, for example H2, CO, N2, methane, hydrogen sulfide, argon, vapors of the solvent used, for example methanol, among other things. The CO content amounts to 0.1%, for example. While it is possible to further lower the content of the pollutants in the washing process, the expenditure (investment costs and operating costs, for example for steam and power consumption) rapidly increases with increasing purity requirements (the production of gas products from raw synthesis gas is described in DE 10 2007 008 690 A1, for example). Removal of CO residues from a CO2 stream is particularly difficult.
DE 10 2407 020 333 A1 describes a method for operation of a dust introduction system for pressurized coal dust gasification, which comprises a storage bunker, dust introduction transfer mechanisms, and a metering vessel. In this connection, heated nitrogen is passed to the bunker, as an inertization and loosening agent, while pressurization of the transfer container and conveying of the dust takes place with pure CO2. The relaxation gas from the transfer container is relaxed and then freed of solids in a filter. In this connection, emptying of the relaxed transfer container into the metering vessel takes place by means of gravity flow.
In DE 36 90 569 C2, a method for removal, from a residual gas, of compounds that contain sulfur is described.
Disadvantages of the known solutions consist, among other things, in that the gas used for transfer and fluidization is allowed to contain only a low concentration of the environmental pollutants CO, H2S, methanol, and others, because it is released into the atmosphere. The transfer based on gravity flow, with the construction of one container on top of another, is complicated because of the great construction height, and has proven to be insufficiently operationally reliable due to compacting of the bulk material. Despite many, extremely varied approaches, it has proven to be extraordinarily difficult to carry out the process of container relaxation in such a gentle manner that internal stresses in the bulk material are kept sufficiently low.